Ajax based chat ?

Results for one to one chat are satisfactory
Chat requires database layer or static data structure
Server will be busy even when there is no message
Peer to peer chat is not possible
File transfer will be slow
File transfer will involve server that requires space and security attentions
Privacy will be an issue as chat logs are stored at server side
HTTP is slower then Sockets due to headers and parsing issues
Transfer of serialized objects is not possible